C500 variants conveying complete mucosal immunity against fatal infections of pigs with Salmonella enterica serovar Choleraesuis C78-1 or F18+ Shiga toxin-producing Escherichia coli

Salmonella enterica serovar Choleraesuis (S. Choleraesuis) C500 strain is a live, attenuated vaccine strain that has been used in China for over 40 years to prevent piglet paratyphoid. However, this vaccine is limited by its toxicity and does not offer protection against diseases caused by F18+ Shiga toxin-producing Escherichia coli (STEC), which accounts for substantial economic losses in the swine industry. We recently generated a less toxic derivative of C500 strain with both asd and crp deletion (S. Choleraesuis C520) and assessed its efficacy in mice. In addition, we demonstrate that C520 is also less toxic in pigs and is effective in protecting pigs against S. Choleraesuis when administered orally. To develop a vaccine with a broader range of protection, we prepared a variant of C520 (S. Choleraesuis C522), which expresses rSF, a fusion protein comprised of the fimbriae adhesin domain FedF and the Shiga toxin-producing IIe B domain antigen. For comparison, we also prepared a control vector strain (S. Choleraesuis C521). After oral vaccination of pigs, these strains contributed to persistent colonization of the intestinal mucosa and lymphoid tissues and elicited both cytokine expression and humoral immune responses. Furthermore, oral immunization with C522 elicited both S. Choleraesuis and rSF-specific immunoglobulin G (IgG) and IgA antibodies in the sera and gut mucosa, respectively. To further evaluate the feasibility and efficacy of these strains as mucosal delivery vectors via oral vaccination, we evaluated their protective efficacy against fatal infection with S. Choleraesuis C78-1, as well as the F18+ Shiga toxin-producing Escherichia coli field strain Ee, which elicits acute edema disease. C521 conferred complete protection against fatal infection with C78-1; and C522 conferred complete protection against fatal infection with both C78-1 and Ee. Our results suggest that C520, C521, and C522 are competent to provide complete mucosal immune protection against fatal infection with S. Choleraesuis in swine and that C522 equally qualifies as an oral vaccine vector for protection against F18+ Shiga toxin-producing Escherichia coli

Room Temperature Surface Modification of Ultrathin FeOOH Cocatalysts on Fe2O3 Photoanodes for High Photoelectrochemical Water Splitting

An ultrathin FeOOH cocatalyst is deposited on α-Fe2O3 photoanodes in a simple room temperature immersion process for efficient photoelectrochemical (PEC) water splitting. The prepared FeOOH/Fe2O3 photoanode has a photocurrent density of up to 2.4 mA/cm2 at 1.23 V versus reversible hydrogen electrode (RHE), and the photocurrent density is increased by about 160% compared to the bare Fe2O3 of 1.55 mA/cm2. An obvious cathodic shift of the photocurrent onset potential from 0.661 to 0.582 V was also observed, and excellent stability was maintained with almost no deterioration for 5 h. The enhanced PEC performance is attributed to the decrease of the interfacial resistance between electrode and electrolyte and the increase of the injection efficiency of holes in Fe2O3

Integration of FexS electrocatalysts and simultaneously generated interfacial oxygen vacancies to synergistically boost photoelectrochemical water splitting of Fe2O3 photoanodes

Integration of FexS electrocatalysts and simultaneously generated interfacial oxygen vacancies (V-O) was designed to promote the water splitting performance of Fe2O3 photoanodes, in which a synergistic effect remarkably reduces the carrier recombination, increases the number of active sites, and facilitates the photogenerated holes to participate in water oxidation

Quasi-Topotactic Transformation of FeOOH Nanorods to Robust Fe₂O₃ Porous Nanopillars Triggered with a Facile Rapid Dehydration Strategy for Efficient Photoelectrochemical Water Splitting

A facile rapid dehydration (RD) strategy is explored for quasi-topotactic transformation of FeOOH nanorods to robust Fe₂O₃ porous nanopillars, avoiding collapse, shrink, and coalescence, and compared with a conventional treatment route. Additionally, the so-called RD process is capable of generating a beneficial porous structure for photoelectrochemical water oxidation. The obtained RD-Fe₂O₃ photoanode exhibits a photocurrent density as high as 2.0 mA cm^–2 at 1.23 V versus reversible hydrogen electrode (RHE) and a saturated photocurrent density of 3.5 mA cm^–2 at 1.71 V versus RHE without any cocatalysts, which is about 270% improved photocurrent density over Fe₂O₃ with the conventional temperature-rising route (0.75 mA cm^–2 at 1.23 V vs RHE and 1.48 mA cm^–2 at 1.71 V vs RHE, respectively). The enhanced photocurrent on RD-Fe₂O₃ is attributed to a synergistic effect of the following factors: (i) preservation of single crystalline nanopillars decreases the charge-carrier recombination; (ii) formation of long nanopillars enhances light harvesting; and (iii) the porous structure shortens the hole transport distance from the bulk material to the electrode–electrolyte interface